Fluid distribution bar



March 11, 1969 R. E. FRAATZ FLUID DISTRIBUTION BAR Sheet 012 Filed Sept.27, 1965 FIG. 3

lNVENTORi ROBERT E. FRAATZ IS AGENT March 11, 1969 R. E FRAATZ 3,431,889

FLUID DI STRIBUTION BAR Filed Sept. 27, 1965 7 Sheet 3. of 2 FIG. 6 FIG.7

PRIOR ART |NVENTOR= ROBERT E. FRAATZ Bnfi H m 10% HIS AGENT UnitedStates Patent Oflice Patented Mar, 11, 1969 3,431,889 FLUID DISTRIBUTIONBAR Robert E. Fraatz, Richmond, Calif., assignor to Shell Oil Company,New York, N.Y., a corporation of Delaware Filed Sept. 27, 1965, Ser. No.490,487 US. Cl. 118-315 5 Claims Int. Cl. B05c 5/00; B05b 7/06 ABSTRACTOF THE DISCLOSURE Apparatus for applying a fluid downwardly onto a flatsurface moving relative to the apparatus. The fluid distribution meanscomprises a horizontal pipe having a plurality of capillary tubing meanspositioned in openings in the pipe and of a length substantially greaterthan their inside diameters.

This invention relates to a machine for applying a coating of liquidmaterial onto flat-surfaced articles passed through a curtain of thecoating material, and more particularly, relates to an improveddistribution means for such a machine when the liquid coating materialforming the curtain is relatively viscous.

When it was necessary to coat flat-surfaced articles, such as plywoodsheets, with a coating of a relatively viscous liquid material forpreservation, or other purposes, it was usually necessary to apply sucha coating by brush or other hand means after the plywood forms and otherstructural members reached their final destinations. The reason for thiswas that no totally satisfactory means was available by which such aviscous coating material could be applied to plywood forms to attain acoating of uniform thickness and composition. For economic reasons, itis desirable to have the coatings as thin as possible. Some commercialmeans for applying such thin coatings to plywood at the mill was needed.This was especially true for coatings of two-component materials wherethe inherent problems are multiplied, e.g., pressures, temperatures,mixing, etc., must be controlled in combination. An example is atwo-component liquid epoxy formulation which, when its components aremixed and applied in one coat, gives a self-oiling, durable plasticcoating. Such a material is sold under the trade mark Shellform T. Themixing and delivery of such twocomponent coating materials to amechanical applicator of any kind is a problem in itself, as isproviding a satisfactory means to flush out such a system to preventclogging of the flow lines upon stoppage in operation. This invention islimited to the application, or distribution means for such a system.

The requirements for such a distribution means are efliciency, economyand simplicity. In the mills, plywood is treated as it is moved along onconveyor belts. It is thus necessary that the distribution means beadapted for this type of operation. The prior art shows many fluiddistributions means which are adapted for use in conjunction withconveyor belts, but which fail to pro duce a satisfactory result whenapplied to the distribution system described for coating plywood with athin layer of an epoxy formulation. Two of the more pertinent patentsare the patents to Florio, No. 3,138,514, issued June 23, 1964 andWrede, No. 1,981,405, issued Nov. 20, 1934. The Florio patent describesa distribution means comprising an elongated tube formed with aplurality of spaced ports, or orifices, which can be modified to producedistinct, continuous streams of adhesive for bonding plies of sheetmaterial. Wrede shows a two-component fluid system for applying glue topasteboard which utilizes a distribution means comprising a pipe withcooperating nozzles. Neither patent discloses a distribution means withthe structural characteristics necessary to provide a thin plywoodcoating of uniform thickness and composition with the liquid coatingmaterials that are commercially desirable.

To develop a distribution means with the necessary structuralcharacteristics, much experimentation was needed. It was found that athroughput range of from 1100-1200 grams/min. was desirable to produce a5 mil coating on 4 x 8 ft. plywood delivered with its length parallel tothe direction of the conveyor at a line speed of about 24 ft./min. Aliquid coating material of the preferred type has viscosity of from 62.to 170 centipoises in a temperature range of from 140 to 110 F. In anelfort to create a curtain of such a coating material using an elongatedpipe with a series of ordinary ports or orifices along the undersidethereof and an operating pressure of less than p.s.i., it was found thatthe fluid would run along the bottom of the pipe forming several largestreams of liquid coming down upon the surface to be coated, rather thana uniform series of streams as required. Going from this type ofarrangement to a distribution means utilizing an elongated pipe withcooperating nozzles as shown in the patents to Florio and Wrede, it wasfound that these also failed to produce a satisfactory flow pattern dueto unequal distribution across the length of the bar. It was necessaryto create a new bar design to handle a problem with which the prior artwas not faced. The new design would have to provide for increaseddistribution pressure across the length of the bar to provide uniformcoating.

The instant invention is directed to this improved structure. This newdistribution bar consists of an elongated pipe with a plurality ofopenings aligned along the underside thereof, to one end of which fluidis supplied from a central distribution block. To create the necessaryhigh resistance across the length of the pipe, capillary tubing with asatisfactory ratio of length to inside diameter is inserted in each ofthese openings. With the use of capillary tubing, a plurality ofdistinct streams is assured at an operating pressure of less than 100psi. to produce a thin coating, e.g., 5 mil, of a relatively viscouscoating material. Since the pressure decreases across the length of thepipe, the spacing between openings can be decreased as the distance fromthe supply end increases, to maintain even distribution.

The invention will be further described with reference to theaccompanying drawings wherein:

FIGURE 1 is a schematic pictorial view showing the distribution means inposition over a conveyor belt for coating sheet-s of plywood;

FIGURE 2 is a plan view of the distribution means;

FIGURE 3 is a detail view of a distribution bar connection;

FIGURE 4 is a frontal view of one of the distribution bars partially insection to show details of the capillary tubing;

FIGURE 5 is a sectional view taken on the line 55 in FIGURE 4;

FIGURE 6 is a sectional view of two standard nozzles of prior designshowing the possible ambulation of fluid streams; and

FIGURE 7 is a sectional view of three capillary tubes of the instantdevice which prevent fluid ambulation.

When applying a thin, uniform coating of a viscous liquid material in adistribution system, it is necessary that suflicient fluid dischargeports be provided so that the entire Width of the surface to be coatedis adequately covered. With a less viscous coating material, this is notas important since the liquid will tend to run more readily across thesurface being coated to fill in larger areas between discharge openings.With the composition of the materials to be used with the instantdevice, it is critical that not only a sufficient number of dischargeopenings be provided, but that each downcoming stream of viscous coatingmaterial be discharged from the distribution means at a specific,predetermined location so as to ensure a uniform coating at an operatingpressure of less than 100 psi. FIGURE 6 shows sectional profiles ofconventional fluid nozzles 6 with fluid ducts 6a in operation anddemonstrates the flow characteristics which develop when an attempt ismade to decrease the spacing between nozzles to provide a greater numberof nozzles per unit of length as is necessary to produce a thin, uniformcoating of viscous material. When the fluid starts to flow from thestandard nozzle, the surface tension of the viscous liquid is such thata liquid layer creeps across the lower discharge end of the nozzleproducing a viscous film 7 by which the drops 8 can ambulate away fromthe discharge opening toward the edges of the nozzle as shown in FIGURE6. The stream of fluid will then flow off the edge of the nozzle ratherthan directly down from the discharge opening. The same process can takeplace at the adjacent nozzle and if the drops ambulate toward the edgeof this nozzle close to the first nozzle so that surface tension dIfilWSthe drops together, the streams from two adjacent nozzles can come downin a single stream away from both discharge openings as shown by dottedlines 9 in FIGURE 6. The process can be multiplied over an entiresection of nozzles so that the flow from several discharge openings forma single stream, producing a coating of viscous material which is toothick in some spots While failing to cover the surface in others. If theslightest tilt exists in the supports for such a distribution means,then the process of fluid stream ambulation will be greatly magnified.This phenomenon can be combatted without altering the design by using anoperating pressure which is sufliciently great enough to actually ejectthe liquid streams from the nozzles with such a force that ambulationwill not occur. It is, however, not desirable to operate at the highpressures required because of additional costs and increased complexityin the system. Even at high pressures, uniform flow across the entirelength of the bar cannot be assured.

FIGURE 7 shows how the use of capillary tubing 10 prohibits theambulation of drops 11 of the viscous coating material and maintainssteady, distinct streams from each of the discharge openings. Thecapillary tubes can be spaced close enough together to achieve a thin,uniform coating of viscous material across the entire width of thesurface coated without having to cope with ambulation of fluid from onepoint on the nozzle tip to another, or from one nozzle to another. Thethin walls of the capillary tubing effectively eliminate this problemensuring a multiplicity of distinct, pre-located, uniform streams.

A schematic pictorial drawing of the distribution means of the instantcase in operation is shown in FIGURE 1. To apply a two-component liquidepoxy formulation comprising components A and B, these components aresupplied under pressure from liquid reservoirs 12 and 13 by means offluid conduits 14 and 15 through valves 16 and 17, respectively, to amixer 18 supported by a cross bar 19. Cross bar 19 is supported over the'working area in any well known manner. Distribution means 20 issuitably supported from cross bar 19 through support means 21. Theflat-surfaced article to be coated, such as plywood 22, is carried by aconveyor belt system 23, only part of which is shown, under thedistribution means 20 which is centered therewith. The distributionmeans 20 comprises a central distribution block 24 connected to supportmeans 21 by a bracket 25 through which passes conduit 26 with valve 27therein which carries the viscous coating mixture from the mixer 18 intothe central distribution block 24 through opening 28 therein (FIGURE 2).Block 24 has a hollow chamber 24a (shown by dotted lines in FIGURE 2)for receiving the mixture from the mixer and two outlet ports, 29 and29a. Distribution or manifold bars 30 and 31 are elongated, horizontalpipes (one of which is shown in FIGURE 4) which are designed to fit intothe outlet ports 29 and 29a, respectively, and remain fixed therein bymeans of rubber O-rings 32 (FIGURE 4) which fit into grooves 33 at oneend of the distribution bars 30 and 31. The ends of the distributionbars 30 and 31 away from the central block 24 are sealed with caps 30aand 31a, respectively. FIGURE 2 shows the distribution bars 30 and 31 inoperative position with respect to the central distribution block 24. Aportion of FIGURE 2 is shown in dotted lines to illustrate onesatisfactory method for connecting the distribution bars 30 and 31 tothe block 24. This construction is shown in greater detail in FIGURE 3.The end of the distribution bar 30 connected to the block 2 4 has acylindrical sleeve 34 fixed within its inside diameter which is machinedto receive an elongated tube 35 attached to the block 24 by acylindrical plug 36 which is fixed therein by Welds 37 and/or a setscrew 38. A fluid passageway 39 within the plug 36 connects chamber 24awith the tube 35. To connect the distribution bar 30 to the block 24, itis only necessary to insert the bar 30 into the outlet port 29 so thatsleeve 34 slides over tube 35 until the end of the bar 30 contacts theplug 36. The bars 30 and 31 are held in position frictionally by meansof the O-ring 32.

In operation, the fluid flows from the supply means into the chamber 24aand then through passageway 39 into tube 35 from which it is dischargedinto the distribution bar for application. The structure and operationfor distribution bar 31 is exactly the same as that described withrespect to bar 30. As shown in FIGURE 4, a plurality of extended liquiddischarge ducts 10 are formed of capillary tubing and aligned along whatbecomes the bottom of the distribution bar when the latter is in itsoperative position, parallel to the central axis thereof. The area 40 ofthe bar surface along which the tubes 10 are aligned may be machined toa flat surface to provide a more convenient surface for drilling theholes and installing the tubing. The relationship between the flatsurface 40 and the capillary tubing 10 is shown in FIG- URE 5, whichalso shows the relative length of the tubing to the exterior wall of thedistribution bar, or pipe 30.

In operation, components A and B of the two-component liquid epoxyformulation are supplied to mixer 18 where they are thoroughly mixedbefore being carried to the distribution means 20. The mixture enterschamber 24a of the central distribution block 24 where it is directedtoward outlet ports 29 and 29a and distribution bars 30 and 31,respectively. The mixture enters the distribution bars and is dischargedthrough the capillary tubing 10 in a plurality of closely spaced butdistinct streams forming a uniform curtain of liquid through which thearticles to be coated pass. It is the high resistance offered by eachindividual capillary tube which provides for the increased distributionpressure across the entire length of the distribution bars. The pressuredrop across the bars is not nearly as great as it would be if standardnozzles were used.

To achieve the desired results, it is necessary that capillary tubinghaving a satisfactory ratio of length to inside diameter be used. Thiscontrols the resistance across the length of the bars. Thus, if it isdesirable to increase the bore Within the capillary tubing, the lengthof the tubing has to be correspondingly increased to compensate for thedecrease in resistance created by a larger fluid discharge opening so asto maintain adequate operating pressure across the bars. To illustratethe criticality of the bar design for achieving satisfactory results,the following test data has been included. Table 1 illustrates thecharacteristics of viscosity vs. temperature of a suitable liquidcoating material, in this case Shellform T mentioned previously.

TABLE 1 Temperature F.): Viscosity (poises) 75 15.00 100 2.75 110 1.70120 1.20 140 0.62 160 0.30

As would be expected, consumption requirements for coating plywood witha 5 mil coating vary proportionally to the line speed. For plywoodsheets 4 ft. in width, about 40-60 grams/min. of coating fluid areapplied for each ft./min. of line speed, e.g., 1510 grams/min. areapplied in a typical operation using a plywood rate of 32 ft./min.

In the desirable application range of 110-140 F. (Table 1), tests wereconducted with a spray bar A which consisted of two 24 in. long sectionsof in. steel pipe (ID=0.39 in.) mounted in an offset manner on a centerdistribution block as previously described. Holes mils in diameter weredrilled on A in. centers across the bars, providing 192 fluid orifices.The results of these tests are given in Table 2.

TABLE 2 Test 011 Bar Flow viscosity pressure (g./min.) Remarks (poise)(p.s.i.)

5. 0 1, 615 Poor distribution pattern. 7. 5 1, 645 Do. 10. 5 1, 675 D0.16. 0 2, 470 D0. 8. 0 1, 320 Do. 6. 0 l, 010 Do.

Thus, spray bar A produced an unsatisfactory spray pattern in thedesired throughput range of 1100-1200 grams/min. -In fact, even at 2500g./min., uneven distributions were observed. Bar pressures ranged from 5to 16 p.s.i. (Table 2). It was obvious that a new bar design was neededin order to increase operating pressure and thus improve the flowdistribution across the bar. Two such bars were designed, built andtested on a laboratory scale set-up. Both utilized the capillary tubingof the instant invention.

Spray bar B consisted of two sections, each 24 in. long, of in. brasspipe, schedule 40 with holes drilled on A; in. centers across the bar,providing 384 orifices total for 2 sections. Into these holes weresoldered 24 gage stainless steel capillary tubing inserts in. long (5mil wall, 22 mil OD and 12 mil ID with variance from 11 to 12.5 mil).The flow characteristics of spray bar B are given in Table 3 at anappropriate operating viscosity.

TABLE 3 Test oil viscosity Bar pressure Flow (g./min.) Remarks (poise)(p.s.i.)

69 1, 440 Good pattern. 58 1, 208 Do. 56 1, 176 Do.

To determine the efiect of non-uniform spacing of the capillary tubes,spray bar C was constructed in exactly the same way except that holeswere drilled on graded centers across the two sections from a spacing of250 mil at the center block to 125 at the ends of the sections providing134 holes in a 2 ft. section, 56 (41.8%) on the half toward the centralblock, 78 (58.2%) on the outer half. The test results for spray bar Care given in Table 4.

TABLE 4 Test oil viscosity Bar pressure Flow (gJmin. Remarks (poise)(p.s.i.) for 4 it.)

36 1, 160 Good pattern. 38 1, 240 Do. 49 628 D0. 56 728 Do. 65 864 Do.79 1, 074 Do.

With bar B (Table 3), flow patterns were excellent at 1100-1200 g./min.and bar pressures of 50-70 p.s.i. were realized. Decreasing the orificediameter from 15 to 12 mils could only partly explain the rise inoperating pressure. Principal cause is theincrease in the orificelength/diameter ratio from 5 to 30 which greatly restricts the flow,improves the exudate pattern and elirninates the mergence of streams.

Similar results were obtained on bar C (Table 4), except that as aresult of the fewer number of orifices, higher head pressures werenecessitated at a fluid viscosity of 1.48 to yield the desired flowrates of 1100-1200 g./min. A distribution study substantiated the theorythat graded centers are necessary to offset the pressure drop across abar. It is evident that for the test conditions, a less severe gradientof 200-125 mils would have led to a better flow pattern. In addition,the spacings between orifices used in this test appears to be excessiveand hinders proper flowout of the coating on the plywood substrate.

Satisfactory results seem to be realized when the length of the tubingis 10 to times as long as its inside diameter. The inside diameter ofthe tubing used during the testing was 0.012 inch while the length was.375 inch giving a ratio of .032 to 1. The cross sectional area of eachtube was about .00112 sq. inch while that of the horizontal pipe in. ID)was about .126 sq. inch. Thus, with 384 tubes, the ratio of totalcapillary tube inside diameter cross sectional area to pipe insidediameter cross sectional area was approximately 1 to 3.

What has been described is an improved distribution means for applying athin coating of a relatively viscous material to flat-surfaced articles.

I claim as my invention:

1. In a machine for applying a viscous fluid in a continuous curtainstream onto a flat, horizontal surface moved relative to said machine, ahigh-pressure fluid distribution system comprising:

(a) fluid supply means;

(b) two elongated, horizontal pipes with a plurality of openings alignedalong the undersides thereof;

(c) capillary tubing positioned in each of said openings and extendingbeyond the exterior wall of the pipes, tforming a row of high resistancefluid ducts with axes normal to the longitudinal axes of the pipes; and

(d) connecting means for attaching the fluid supply means to thehorizontal pipes, said pipes being parallel and offset from one anotherso as not to overlap.

2. A high-pressure distribution system for viscous fluids as defined inclaim 1 wherein the fluid supply means is centered between said twopipes and attached to one end of each of the pipes through saidconnecting means and the spacing between adjacent openings is graduatedalong the length of the pipes, varying from a maximum value at the endsof the pipes attached to the fluid supply means to a minimum value atthe opposite ends thereof.

3. In the machine of claim 1 wherein the length of the capillary tubingpositioned in each of said openings is from 10 to 100 times as long asthe inside diameter of said tubing.

4. In the machine of claim 1, wherein said connecting means is disposedat one end of said'horizontal pipes and the spacing between adjacentopenings in said horizontal pipes is graduated along the length of saidpipes, varying from a maximum value at the end to which the fluid supplymeans is conected to the horizontal pipes to a minimum value at theopposite end thereof.

5. In the machine of claim 1 wherein the ratio of total cross-sectionalarea of the inside diameter of said capillary tubing to thecross-sectional area of the inside diameter of said pipes isapproximately 1 to 3.

References Cited UNITED STATES PATENTS 2,543,013 2/1951 Glassey 1184012,733,171 1/19'56 Ransburg 118315 X 5 3,059,610 10/1962 Mentz 118-315 X3,256,581 6/1966 Thal et al. 11831S X WALTER A. SCHEEL, PrimaryExaminer.

10 ROBERT I. SMITH, Assistant Examiner.

